CVE-2026-43205: Linux Kernel Buffer Overflow Vulnerability

CVE-2026-43205 Overview

CVE-2026-43205 is an out-of-bounds write vulnerability in the Linux kernel's dpaa2-switch driver. The driver retrieves sw_attr.num_ifs from firmware via dpsw_get_attributes() but fails to validate the value against DPSW_MAX_IF (64). This unchecked value drives iteration in dpaa2_switch_fdb_get_flood_cfg(), which writes port indices into the fixed-size cfg->if_id[DPSW_MAX_IF] array. When firmware reports num_ifs >= 64, the loop writes past the array bounds, corrupting adjacent kernel memory.

Critical Impact
A compromised or malicious firmware reporting num_ifs >= 64 triggers a kernel-space out-of-bounds write, leading to memory corruption and potential denial of service or privilege escalation on systems using the dpaa2-switch driver.

Affected Products

Linux kernel versions containing the dpaa2-switch driver prior to the patches referenced in the kernel.org advisories
Systems running NXP DPAA2 (Data Path Acceleration Architecture) Ethernet switch hardware
Embedded and networking platforms using the drivers/net/ethernet/freescale/dpaa2 switch driver

Discovery Timeline

2026-05-06 - CVE-2026-43205 published to NVD
2026-05-06 - Last updated in NVD database

Technical Details for CVE-2026-43205

Vulnerability Analysis

The dpaa2-switch driver manages NXP Data Path Acceleration Architecture v2 Ethernet switch interfaces. During initialization, the driver calls dpsw_get_attributes() to obtain switch configuration from firmware, including the num_ifs field that indicates the number of switch interfaces. The driver trusts this value implicitly and uses it to drive iteration over fixed-size kernel arrays.

The critical code path resides in dpaa2_switch_fdb_get_flood_cfg(). This function iterates num_ifs times, populating the cfg->if_id[] array, which is sized at DPSW_MAX_IF (64) entries. After the main loop, the function appends the control interface index at position num_ifs. When num_ifs == 64, this trailing write overflows the array by one entry. When num_ifs > 64, the main loop itself overflows multiple entries.

A secondary defense in build_if_id_bitmap() silently drops any ID greater than or equal to 64, but this protection executes after the corrupting writes have already occurred.

Root Cause

The root cause is missing input validation [CWE-787 Out-of-Bounds Write] on firmware-supplied data. The driver does not enforce that num_ifs < DPSW_MAX_IF before using the value as a loop bound. The fix adds a bound check using >= rather than > because num_ifs == DPSW_MAX_IF is also functionally broken due to the trailing control-interface write.

Attack Vector

Exploitation requires the firmware to report a malformed num_ifs value of 64 or greater. This is not directly reachable from unprivileged userspace. The threat model covers compromised firmware, malicious hardware, supply-chain attacks against DPAA2 firmware images, or developer error during firmware modification. Successful exploitation results in kernel heap or stack corruption depending on the allocation context of cfg.

Code-level exploitation details are described in the upstream commits. See the kernel.org commit references for the validating patch.

Detection Methods for CVE-2026-43205

Indicators of Compromise

Kernel oops or panic messages referencing dpaa2_switch_fdb_get_flood_cfg or dpaa2_switch_init in dmesg or system logs
KASAN (Kernel Address Sanitizer) reports of out-of-bounds writes within the dpaa2 switch driver call path
Unexpected dpaa2-switch driver initialization failures or num_ifs values exceeding 64 in driver debug output

Detection Strategies

Audit running kernel versions on DPAA2-equipped hardware against the patched commit hashes published on kernel.org
Enable KASAN or KFENCE on test systems running the dpaa2-switch driver to catch out-of-bounds writes during fuzzing of firmware-supplied attributes
Monitor kernel logs for warnings introduced by the validation patch when firmware reports invalid num_ifs values

Monitoring Recommendations

Centralize kernel log collection from embedded networking platforms and alert on dpaa2-switch initialization errors
Track kernel package versions across the fleet and flag systems lagging behind upstream stable releases
Validate firmware images for DPAA2 hardware against known-good vendor checksums before deployment

How to Mitigate CVE-2026-43205

Immediate Actions Required

Update affected Linux kernels to a stable release containing the dpaa2-switch: validate num_ifs to prevent out-of-bounds write fix
Inventory all systems using NXP DPAA2 switch hardware and prioritize patching of production networking gear
Verify firmware integrity on DPAA2 platforms and restrict firmware update channels to trusted vendor sources

Patch Information

The upstream fix adds a bound check for num_ifs against DPSW_MAX_IF in dpaa2_switch_init(), rejecting any value greater than or equal to 64. The fix has been backported across multiple stable trees. Review the following commits: 89764cf44544, 8a5752c6dcc0, 8b841fd529db, a26dda3bae46, a3034a8d5617, b690635d4719, and c18493f75020.

Workarounds

If patching is not immediately possible, blacklist the dpaa2-switch kernel module on systems where switch functionality is not required
Restrict physical and management access to DPAA2 hardware to prevent firmware tampering
Pin firmware images to verified versions and disable runtime firmware reload paths where feasible

bash

# Blacklist the dpaa2-switch module until patches are applied
echo "blacklist dpaa2_switch" | sudo tee /etc/modprobe.d/blacklist-dpaa2-switch.conf
sudo update-initramfs -u

# Verify running kernel version against patched stable releases
uname -r

# Check if dpaa2-switch is currently loaded
lsmod | grep dpaa2_switch